Lead-free solder compositions

- Ford

Electrical solder compositions (by weight percent) having between 91.5-96.5% Sn; 2-5% Ag; 0.1-3% Ni; and 0-2.9% Cu; and having a melting temperature 220.degree. C. or less. The solder compositions have microstructure with uniformly dispersed fine grains of Sn--Ni, Sn--Cu and Sn--Cu--Ni intermetallic phases that provide resistance to grain growth during thermal cycling.

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Claims

1. An electrical solder composition consisting essentially of:

between 91.5-96.5% Sn;
2-5% Ag;
0-2% Cu;
0.1-2% Ni and
having a melting temperature 220.degree. C. or less.

2. The electrical solder composition of claim 1, wherein said composition is about:

96.5% Sn;
3% Ag;
0.5% Ni and
having a Sn--Ag eutectic microstructure and dispersed small needle-shaped grains of Sn--Ni intermetallic phase.

3. The electrical solder composition of claim 1, wherein said composition of claim 1, wherein said composition is about:

96.5% Sn;
2.5% Ag;
1.0% Ni and
having a Sn--Ag eutectic microstructure and dispersed small needle-shaped grains of Sn--Ni intermetallic phase.

4. The electrical solder composition of claim 1, wherein said composition is about:

96.5% Sn;
2.5% Ag;
0.5% Cu;
0.5% Ni and
having a Sn--Ag eutectic microstructure and dispersed small grains of Sn--Cu intermetallic phase and small grains of Sn--Ni--Cu intermetallic phase.

5. The electrical solder composition of claim 1, wherein said composition is about:

96.0% Sn;
2.0% Ag;
1.0% Cu;
1.0% Ni and
having a Sn--Ag eutectic microstructure and dispersed small grains of Sn--Cu intermetallic phase and large grains of Sn--Ni--Cu intermetallic phase.

6. The electrical solder composition of claim 1, wherein said composition is about:

95.0% Sn;
3.0% Ag;
1.0% Cu;
1.0% Ni and
having a Sn--Ag eutectic microstructure and dispersed small grains of Sn--Cu intermetallic phase and platelets of Sn--Ni--Cu intermetallic phase.

7. The electrical solder composition of claim 1, wherein said composition is about:

94.0% Sn;
2.0% Ag;
2.0% Cu;
2.0% Ni and
having a Sn--Ag eutectic microstructure and dispersed small grains of Sn--Cu intermetallic phase and larger platelets of Sn--Ni--Cu intermetallic phase.

8. An electrical solder composition consisting essentially of about:

96.5% Sn;
2.5% Ag;
0.5% Ni;
0.5% Cu and
having a melting temperature 220.degree. C. or less.
Referenced Cited
U.S. Patent Documents
1565115 December 1925 Speed et al.
3157473 November 1964 Reginald
3503721 March 1970 Lupfes
3607253 September 1971 Cain
4011056 March 8, 1977 Steine et al.
4214903 July 29, 1980 Murabayashi et al.
4643875 February 17, 1987 Mizuhara
4758407 July 19, 1988 Ballentine et al.
4797328 January 10, 1989 Boehm et al.
4806309 February 21, 1989 Tulman
5328660 July 12, 1994 Gonya et al.
5344607 September 6, 1994 Gonya et al.
5429689 July 4, 1995 Shangguan et al.
5455004 October 3, 1995 Slattey et al.
Foreign Patent Documents
3830694 A1 March 1990 DEX
08001373 January 1996 JPX
Patent History
Patent number: 5863493
Type: Grant
Filed: Dec 16, 1996
Date of Patent: Jan 26, 1999
Assignee: Ford Motor Company (Dearborn, MI)
Inventors: Achyuta Achari (Canton, MI), Mohan R. Paruchuri (Canton, MI), Dongkai Shangguan (Novi, MI)
Primary Examiner: Sikyin Ip
Attorney: Damian Porcari
Application Number: 8/771,351